1. Field of the Invention
The present invention relates to a travelling vehicle system for carrying a cargo along a track to transfer the cargo to a rack or the like.
2. Description of the Related Art
There has hitherto been known a travelling vehicle system for allowing a travelling vehicle to travel along a track hung on a ceiling to carry a cargo in the vicinity of the ceiling. The travelling vehicle is provided with a lift stage liftably hung by means of a hanging member. The travelling vehicle transfers the cargo by lowering the lift stage to a placement member of a rack arranged along a travelling route of the travelling vehicle.
The track is installed in accordance with arrangement of the rack. The travelling route formed by the track typically includes a branching part and a merging part . In the branching part and the merging part, a switching track for connecting one track to one of a plurality of tracks is provided. The travelling vehicle selects a travelling route in accordance with a cargo loading/unloading instruction, to load and unload a cargo.
Herein, the travelling vehicle system has a configuration to prevent entry of a travelling vehicle into the switching track, for example, when a track on which the travelling vehicle is currently travelling is not coupled with a track selected by the travelling vehicle (e.g., see Japanese Unexamined Utility Model Application Publication No. 07-6029). The travelling vehicle needs to wait at a position before the track until a permission to enter the switching track is issued by the host controller.
However, in the case of waiting before the switching track, a space for allowing the travelling vehicle to wait is required before the switching track. In this case, there is a problem of limitations on flexibility in design of the track.
The present invention has been made in view of the above problem, and has an object to provide a travelling vehicle system capable of improving flexibility in design of a track.